The present invention relates to an apparatus for transporting a continuous web, and for manipulating the web especially to form web loops. The apparatus is particularly useful in the manufacture of disposable absorbent articles, including diapers, adult incontinence products, sanitary napkins and the like.
Manufacturing processes are often required to provide discrete strips of a material onto a continuous web, in such a way that the discrete webs of material are spaced apart along the length of the continuous web. Features manufactured in this way include elastic strips, one example of which is the elastic leg cuffs applied to diapers.
U.S. Pat. No. 4,081,301, issued on March 1978, discloses a process for applying a material, such as an elastic material, to a continuous web. The material is only glued along the length of the web in discrete sections, so that when the web is cut the elastic material remains extended only in the discrete section in which it has been glued, and contracts elsewhere.
U.S. Pat. No. 4,227,952, issued on Oct. 14th 1980, discloses a conveyor which carries spaced web support plates and wherein a continuous web is tucked in between the support plates to form web loops is known. Various features, such as leg elastic, are then applied to the web which lies on the web support plate, but not to the web loop. This forming process requires less elastic material and provides material savings.
An apparatus of this type comprises a plurality of web support plates, each web support plate having an outer web support surface. However the apparatus is mechanically complex and not well-suited to high speed manufacturing machines.
The object of the present invention is to provide a mechanically simpler and more reliable apparatus for applying features, including elastic features, to a continuous web, in particular on a high speed manufacturing machine.
A further object of the invention is to provide a process for transporting and manipulating a web using the apparatus of the invention.
The object of the invention is achieved by an apparatus comprising a plurality of means for forming web loops, each means for forming web loops being positioned between adjacent web support plates, wherein each of the web support surfaces lies in an arc, the arcs lying around the circumference of a circular path, and wherein the web support surfaces and means for forming web loops are rotatably mounted about the axis of the circular path. In a preferred embodiment of the invention, the means for forming web loops is provided by rotatably driving the web support plates around the circular path with a circumferential velocity, wherein the circumferential velocity is varied between a minimum circumferential velocity and a maximum circumferential velocity so that the distance between adjacent web support plates varies between a minimum distance and a maximum distance. Preferably the circumferential velocity of the web support plates varies according to a sinusoidal function, and wherein one cycle of the sinusoidal function corresponds to one complete rotation of the web support plate around the circular path.
The invention also relates to a process for transporting a continuous web around the apparatus whereby the distance between adjacent web support plates is greater than the minimum distance, and wherein the web is transported around the circular path so that a web loop is formed when the distance between adjacent web support plates decreases towards the minimum distance.